1. Field of the Invention
The present invention relates to a microtip employed in a surface-observing apparatus such as a scanning tunneling microscope (hereinafter referred to as STM) and a high-density recording-reproducing apparatus for detecting electric current, extremely small force, and the like. The present invention also relates to a process for preparing the microtip, and a surface-observing apparatus and a high density recording-reproducing apparatus employing the microtip.
2. Related Background Art
Microtip used in STM or the like are mostly prepared conventionally from material such as a tungsten wire or platinum wire by mechanical grinding by means of a diamond drill or the like, or electrochemical etching, in a shape of a sharp tip. Recently, a cleavage method has been reported which utilizes the properties of a single crystal material (Yada, et al.: "Observation of Surface Atomic Image with a Scanning Tunneling Microscope, and Material of Tip Therefor", Shinku (Vacuum) Vol. 31, No. 5, 1988).
The prior art techniques of producing the microtips have disadvantages below:
1. Electrochemical etching causes formation of an oxide film on the surface of the tip, which makes it impracticable to measure precisely a minute tunneling current in STM. Moreover, this method provides a microtip having low mechanical rigidity owing to the small solid angle of the tip.
2. Mechanical grinding is liable to apply excessive stress to the material and is not satisfactory in control of the shape of the tip because of the mechanical cutting.
3. The cleavage method does not always give the desired sharp solid angle, and is not sufficient in reproducibility in the production.
4. The microtips produced according to the above prior art techniques, do not exhibit stability and reliability in image observation, writing, and reading when they are used for a surface-observing apparatus or a recording-reproducing apparatus.